1. Field of the Invention
The present invention relates to an absorbent article capable of absorbing and retaining liquids discharged from the wearer""s body such as typically menses and others. More particularly, it relates to an absorbent article capable of reducing a wet feel between the wearer""s skin and leakage-preventing side walls of the article so as not to give an unpleasant feel to a wearer.
2. Description of the Related Art
Various absorbent articles such as sanitary napkins, incontinence pads, disposable diapers and others have heretofore been developed and known. These absorbent articles comprise a liquid-impermeable backsheet, a liquid-permeable topsheet, and an absorbent core between the topsheet and backsheet, and have leakage-preventing side walls extending in the longitudinal direction of the article on the two sides of the absorbent core.
The leakage-preventing side walls are made of a nonwoven fabric comprising mainly hydrophobic synthetic fibers. In the leakage-preventing side walls made of such a nonwoven fabric of hydrophobic synthetic fibers, the liquid retentiveness of the fibers themselves is low. Accordingly, when kept in contact with a large amount of liquid, the leakage-preventing side walls are highly resistant to liquid permeation, and therefore can prevent the liquid from leaking out of them.
On the other hand, Japanese Unexamined Patent Publication No. 322877/1996 discloses leakage-preventing side walls made of a plastic sheet. The leakage-preventing side walls made of a plastic sheet disclosed are also highly resistant to liquid permeation.
However, in the leakage-preventing side walls made of a nonwoven fabric comprising mainly the hydrophobic synthetic fibers, the liquid retentiveness of the fibers themselves that constitute the nonwoven fabric is low, and the fibers have almost no capillary action. Therefore, a small amount of body fluid or sweat having been once adhered to the surface of the leakage-preventing side walls is difficult to move therefrom. As a result, such a small amount of liquid will often remain between the wearer""s skin and the leakage-preventing sidewalls, and therefore gives a wet feel to a wearer.
On the other hand, the leakage-preventing side walls made of a plastic sheet often stick tightly to the wearer""s skin, and therefore a small amount of body fluid or sweat is apt to remain between their surface and the wearer""s skin. As a result, the surface of the leakage-preventing side walls has a sticky feel and gives an unpleasant feel to a wearer. In addition, the leakage-preventing side walls made of a plastic sheet are poorly pervious to vapor, and they are apt to give a stuffy feel.
The present invention has been worked out in view of the shortcoming in the prior art set forth above. It is therefore an object of the present invention to provide an absorbent article provided with leakage-preventing side walls which are highly resistant to liquid and have the ability to absorb a small amount of liquid and which hardly give a wet feel to a wearer.
According to the present invention, there is provided an absorbent article comprising a topsheet, a backsheet and an absorbent core positioned between the topsheet and the backsheet, and having leakage-preventing side walls on a liquid-receiving side of the article, the leakage-preventing side walls extending in a longitudinal direction of the article and lying opposite one another in a width direction of the article, wherein
at least a liquid-receiving face of each leakage-preventing side wall is made of a fibrous sheet that contains hydrophobic fibers thermally bonded to one another and hydrophilic fibers shorter than the hydrophobic fibers, and at least a part of the hydrophilic fibers form aggregates which are dispersed in the fibrous sheet and are bonded to the hydrophobic fibers.
When the fibrous sheet comprises an outer layer and an inner layer in section with respect to the thickness thereof, it is desirable that the hydrophilic fiber aggregates are not in the outer layer but are only in the inner layer. In this case, if the basis weight of the fibrous sheet falls between 20 and 60 g/m2, and if the basis weight of the outer layer of the fibrous sheet falls between 5 and 15 g/m2, the distance between the liquid-receiving face of the side wall and the hydrophilic fiber aggregates existing in the side wall can be shortened so that the hydrophilic fiber aggregates can readily absorb the moisture having adhered to the outer layer of the fibrous sheet.
The fibrous sheet may have a plurality of apertures formed therein. Preferably, the fibrous sheet is folded back at the top of the side wall. If desired, it may be folded twice or more. A liquid-absorbent layer may be disposed between the confronting faces of the thus-folded fibrous sheet.
Also preferably, the fiber density of the hydrophilic fiber aggregates is higher than the fiber density of a portion of the fibrous sheet not containing the aggregates therein. More preferably, the fiber density of the hydrophilic fiber aggregates falls between 1.5 and 3 times the fiber density of the portion of the fibrous sheet not containing the aggregates therein.
For example, the hydrophobic fibers have a length of from 38 to 64 mm, and the hydrophilic fibers have a length of from 5 to 25 mm. Preferably, the length of the hydrophilic fibers is at most xc2xd of that of the hydrophobic fibers. If the fiber lengths are within the ranges, the hydrophilic fibers can be readily massed or crimped to form the aggregates and dispersed among the hydrophobic fibers by using a conventional carding unit.
Also preferably, the fibrous sheet contains from 70 to 98% by weight of hydrophobic fibers and from 2 to 30% by weight of hydrophilic fibers. When the amount of the hydrophilic fibers in the fibrous sheet is at most 30% by weight, more preferably at most 10% by weight, the hydrophilic fiber aggregates can be well dispersed in the fibrous sheet while being suitably spaced from each other therein.
In the absorbent article of the invention, the fibrous sheet (e.g., nonwoven fabric) for forming the leakage-preventing side wall comprises mainly the hydrophobic fibers thermally bonded to one another and contains the hydrophilic fibers which are massed or crimped to form the aggregates having a higher density and are dispersed in the fibrous sheet. When a small amount of liquid or sweat is given to the leakage-preventing side walls, it is well retained by the hydrophilic fiber aggregates having a higher density and dispersed therein, owing to their hydrophilic capillary action. Accordingly, the small amount of liquid having been given to the side walls remains little in the space between the hydrophobic fibers therein, and therefore returns little to the wearer""s skin. Therefore, the surface of the leakage-preventing side wall can be readily kept dry and hardly gives a wet feel to the wearer""s skin.